[Taxacom] Just one species of Bromeliales in Africa

[John Grehan]

Here Ken has moved away from asking questions to his usual acceptance of
dispersal "suggestions" as somehow having empirical content and then
discussing the likelihood of dispersal as if any of this had any
reality. 

If Dick et al demonstrate a recent divergence between African and
American bromeliads that is one thing, but if it is the usual molecular
dispersalist garbage of asserting a recent origin from a minimal
divergence estimate, or some other similar dispersalist assumption, then
that is another matter entirely and it would no more preclude an early
origin than for the dragonflies.

Of course Ken is no doubt familiar with the general biogeographic
significance of Fouta Djalon.

John Grehan



-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth Kinman
Sent: Monday, October 17, 2011 12:19 AM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Just one species of Bromeliales in Africa

Hi Geoff,
      I think you are correct, and that Pitcairnia feliciana was
collected somewhat inland (not coastal).  But I am still surprised that
it has not been found in other countries in western Africa. If the
Rapateaceae species dispersed earlier as suggested, perhaps competitive
exclusion could be a possibility.   In any case, I just found a paper by
Dick et al., 2007 (Molecular Ecology 16:3039-3049) which suggests that
this Pitcairnia species and the Rapateaceae genus dispersed across the
Atlantic by very strong wind currents (perhaps along with a few other
plant species).     

      Not sure if dispersal by strong winds is more likely than
dispersal by birds in these cases, but more cases of plant species being
dispersed from northern South America to this area in equatorial west
Africa are slowly being discovered.  And these are relatively late
events (within in the last 12 million years), completely different from
the vicariance event which resulted in the damselfly genera discussed
earlier (which diverged FAR FAR earlier, on the order of 150 million
years ago).      
      So I continue to believe that vicariance (which is supported in
many cases for genera and higher level taxa) has been invoked too often
for some species level events.  Thus my earlier frustration that some
would jump on a species level dispersal in the opposite direction (Nile
crocodiles from Africa to South America), suggesting vicariance in that
case merits serious consideration (due to their excessive distrust of
molecular clocks and molecular data in general).  Although I frankly
don't think molecular clocks are nearly as regular as some might think,
I also think that the opposite view (dismissing and trashing such data
as often as possible) is even less helpful.
        -------------Ken



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